Solid dry flowable materials comprise dry, solid particles of sufficient average size that the effect of their weight exceeds surface effects that can cause interparticle attraction and susceptibility to air currents, thereby allowing the particles to flow and be poured, similar to a liquid, such as from container to container. The average size needed for such flowability depends upon a variety of factors including particle density and susceptibility to electrostatic attraction, but typically solid dry flowable materials comprise particles with mean diameters of at least about 100 μm.
Solid dry flowable materials (alternatively referred to simply as “dry flowable materials”) include a wide variety of important commodities, including table salt, granulated sugar, sand, gravel, pellets of bulk thermoplastics, etc. For agrochemicals including crop protection agents, such as herbicides, fungicides, bactericides, arthropodicides, nematocides and molluscicides, and also nutrients such as fertilizers, dry flowable compositions have become a favored physical form for active ingredients with physical properties conducive to solid formulation. Like dusts and wettable powders, dry flowable compositions tend to have excellent shelf-life characteristics. Unlike dusts and wettable powders, the granule particles in dry flowable compositions can be easily transferred by pouring, leave little residue in containers, and are generally non-dusty, minimizing possible environmental contamination and inhalation or other exposure hazards. Dry flowable compositions of crop protection agents are also often designed to be water dispersible so that the granule particles break up and disperse on contact with water to form suspensions or solutions for application. Dry flowable compositions of agrochemicals can be prepared by a variety of manufacturing techniques, including fluid bed granulation, pan granulation, spray drying, intensive mixing, paste extrusion, heat extrusion and compaction.
Because dry flowable compositions of agrochemicals are so readily transferable between containers, they facilitate dispensing even relatively large quantities at locations remote from the site of formulation manufacturing. Such remote locations may include distributors' warehouses and farmers' fields. However, particularly because of the high biological activity of agrochemicals, suitable dispensing equipment is needed to ensure amounts of the desired agrochemicals are accurately measured and dispensed, and workers and the environment are not inadvertently contaminated.
U.S. Pat. No. 5,738,153 discloses an apparatus for measuring and dispensing solid dry flowable materials, comprising a refill container containing bulk material, a hopper connected to the refill container by a transfer valve, a transfer container, a control valve to regulate material flow between the hopper and the transfer container, a weighing device supporting the transfer container, and a means for identifying both the refill container and the transfer container to regulate the flow of material between the refill container, hopper and transfer container. This apparatus thus relies upon weighing the transfer container to determine the amount of solid dry flowable material dispensed into the container. While this works well for many needs, particularly with low-use-rate crop protection agents, the required transfer container and weighing device for supporting the transfer container result in some limitations. With agrochemicals entailing high use rates, the appropriately sized transfer container becomes large and heavy when filled, and thus more difficult to handle. Furthermore it may be more expedient to dispense measured quantities of a dry flowable formulation directly into apparatus not comprising a transfer container that can be readily weighed, e.g., a transporting system, a drum for mixing with other agrochemical formulations or a spray tank. For these reasons, an apparatus or system for measuring and dispensing solid dry flowable materials without relying on weighing a transfer container is needed.